In recent years, adhesives essentially comprising inorganic ingredients have been studied. For Example, Japanese Patent Publication 33510/75 discloses a process for producing a highly heat-resistant adhesive composition, comprising calcining a mixture of a particulate high-purity zirconium oxide and colloidal silicic acid as well as sodium aluminate in an amount of 2 to 10% by weight of the total amount of the zirconium oxide and the silicic acid at 1,000.degree. C. or more and finely pulverizing the calcined material. It was reported that the adhesive produced in this process has a lower curing temperature in a range of 250.degree. to 350.degree. C.
The present inventors has succeeded in significantly improving the life of a mold by affixing or applying a heat resistant fiber such as potassium titanate (K.sub.2 Ti.sub.6 O.sub.13) fiber, polytitanocarboxyl silane fiber and carbon fiber onto an inner surface of the mold by use of such inorganic adhesive composition (see Japanese Patent Application Nos. 313755/88 and 323607/88 (Laid Open Publication No. 169150/91). They have also provided a heat resistant sheet using the above-described adhesive composition (see Japanese Patent Application No.13308/89).
However, the present inventors have understood that the above-described adhesive composition has a problem in its stability after being cured, and the cured coating film is liable to be relatively peeled off. Thereupon, as a result of repeated studies to improve the stability, it has been found that the addition of yttria provides an adhesive film (or coating film) which exhibits a more excellent stability than the adhesive described in Japanese Patent Publication 33510/75 and has significant excellent wear resistance, peel-off stability and thermal shock resistance after being dried.